Method RewindBlockIndex

src/validation.cpp:4417–4506

}

bool CChainState::RewindBlockIndex(const CChainParams& params)
{
    LOCK(cs_main);

    // Note that during -reindex-chainstate we are called with an empty chainActive!

    int nHeight = 1;
    while (nHeight <= chainActive.Height()) {
        // Although SCRIPT_VERIFY_WITNESS is now generally enforced on all
        // blocks in ConnectBlock, we don't need to go back and
        // re-download/re-verify blocks from before segwit actually activated.
        if (IsWitnessEnabled(chainActive[nHeight - 1], params.GetConsensus()) && !(chainActive[nHeight]->nStatus & BLOCK_OPT_WITNESS)) {
            break;
        }
        nHeight++;
    }

    // nHeight is now the height of the first insufficiently-validated block, or tipheight + 1
    CValidationState state;
    CBlockIndex* pindex = chainActive.Tip();
    while (chainActive.Height() >= nHeight) {
        if (fPruneMode && !(chainActive.Tip()->nStatus & BLOCK_HAVE_DATA)) {
            // If pruning, don't try rewinding past the HAVE_DATA point;
            // since older blocks can't be served anyway, there's
            // no need to walk further, and trying to DisconnectTip()
            // will fail (and require a needless reindex/redownload
            // of the blockchain).
            break;
        }
        if (!DisconnectTip(state, params, nullptr)) {
            return error("RewindBlockIndex: unable to disconnect block at height %i (%s)", pindex->nHeight, FormatStateMessage(state));
        }
        // Occasionally flush state to disk.
        if (!FlushStateToDisk(params, state, FlushStateMode::PERIODIC)) {
            LogPrintf("RewindBlockIndex: unable to flush state to disk (%s)\n", FormatStateMessage(state));
            return false;
        }
    }

    // Reduce validity flag and have-data flags.
    // We do this after actual disconnecting, otherwise we'll end up writing the lack of data
    // to disk before writing the chainstate, resulting in a failure to continue if interrupted.
    for (const auto& entry : mapBlockIndex) {
        CBlockIndex* pindexIter = entry.second;

        // Note: If we encounter an insufficiently validated block that
        // is on chainActive, it must be because we are a pruning node, and
        // this block or some successor doesn't HAVE_DATA, so we were unable to
        // rewind all the way.  Blocks remaining on chainActive at this point
        // must not have their validity reduced.
        if (IsWitnessEnabled(pindexIter->pprev, params.GetConsensus()) && !(pindexIter->nStatus & BLOCK_OPT_WITNESS) && !chainActive.Contains(pindexIter)) {
            // Reduce validity
            pindexIter->nStatus = std::min<unsigned int>(pindexIter->nStatus & BLOCK_VALID_MASK, BLOCK_VALID_TREE) | (pindexIter->nStatus & ~BLOCK_VALID_MASK);
            // Remove have-data flags.
            pindexIter->nStatus &= ~(BLOCK_HAVE_DATA | BLOCK_HAVE_UNDO);
            // Remove storage location.
            pindexIter->nFile = 0;
            pindexIter->nDataPos = 0;